Issues with apps loading in browser

[delirium]

Hi all,

For the past couple of days, maybe a week, I'm having weird issues with the apps loading in the browser. The apps I'm refering to are Sonarr, Radarr, Jackett, Plex and Qbittorrent.
When I attempt to open the web page, they just get stuck on "Waiting domain" or "Waiting IP" (if I open them with the local IP address). When I refresh the page a couple of times (hit Cltr+R/Ctrl+F5) it finally loads. The actual NAS web interface works without any issues.

I've double/tripple checked the NW connectivity, DNS settings, rebooted, checked HW, checked temperatures... everything I can think of, but nothing seems to have resolved the issue.
Has onyone experienced such issues? What could the reason be?

The NAS is a TVS-473 8GB model.
Firmware version 4.5.3.1697 Build 20210611